The colorimeter measures the transmitted light, calculates the absorbance value, and uses this to determine the unknown concentration. Colorimetry is the science of the measurement of color. It involves measuring the concentration of a colored compound in a solution and the reflected or transmitted light of a solid transparent or. Colorimetric assays are analytical techniques that measure the concentration of a substance in a sample by detecting and quantifying changes in color produced during a chemical reaction specific to the analyte of interest.